Variable Capacity Vane Pump

ABSTRACT

In a variable capacity vane pump, a space between adjacent vanes is 1 pitch. A line that connects a half-pitch-advanced position from an end edge of an inlet port or from an end edge of an outlet port and a driving shaft center in a no-load state is termed a port reference line. A line that connects a center of a cam ring inner circumference side and the driving shaft center when an eccentricity amount of a cam ring is a maximum is termed a high pressure cam profile reference line. A line that connects the center of the cam ring inner circumference side and the driving shaft center at a low pressure when the eccentricity amount of the cam ring is a minimum is termed a low pressure cam profile reference line. The three reference lines; the port reference line, the high pressure cam profile reference line and the low pressure cam profile reference line, is set to be substantially parallel to each other.

TECHNICAL FIELD

The present invention relates to a variable capacity pump, and moreparticularly to a variable capacity vane pump for power steering.

BACKGROUND ART

A conventional variable capacity vane pump which is disclosed in aPatent Document 1 controls a pump discharge amount by rocking a camring.

-   Patent Document 1: Japanese Patent Application Kokai Publication No.    2005-42675

SUMMARY OF THE INVENTION

However, in the above conventional art technique, unlike a fixedcapacity type pump, since this pump has an inlet port and an outletport, pressure is in an unbalanced state in which a pressure of anoutlet port side is greater.

This outlet port side pressure acts on a rotor and a driving shaft, andbends and shifts the driving shaft to an inlet port side, then thedriving shaft is offset. This causes a deviation of switch betweensuction and discharge. In the conventional art technique, since both ofa center of the cam ring and a center of the driving shaft in a no-loadstate are set on a change line (a port reference line) on which thesuction and the discharge are switched, a delay of a start timing ofcompression occurs due to the shift of the driving shaft, and there is aproblem that causes a decrease in pump efficiency and causesoscillation.

The present invention focuses attention on this problem, and an objectof the present invention is to provide a variable capacity vane pumpthat is capable of reducing the decrease in pump efficiency and theoscillation.

In order to achieve the above object, in the present invention, avariable capacity vane pump comprises: a pump body; a driving shaftrotatably supported by the pump body; a rotor provided in the pump bodyand rotatably driven by the driving shaft; a plurality of vanes radiallyextendably installed in their respective slots that are arranged in acircumferential direction in the rotor; a cam ring rockably provided ona supporting surface with a rock fulcrum being a center in the pump bodyand formed into a ring shape also forming a plurality of pump chambersat an inner circumference side of the cam ring in cooperation with therotor and the vanes; first and second members provided at both sides inan axial direction of the cam ring; an inlet port provided at least oneof the first and second members and opening to a section of the pumpchamber where a volume of the pump chamber increases; an outlet portprovided at least one of the first and second members and opening to asection of the pump chamber where the volume of the pump chamberdecreases; and a seal member provided at an outer circumference side ofthe cam ring and defining a first hydraulic pressure chamber located ata side where a pump discharge amount increases and a second hydraulicpressure chamber located at a side where the pump discharge amountdecreases in a space outside the outer circumference of the cam ring,and a space between adjacent vanes of the plurality of vanes is 1 pitch,a line that connects a half-pitch-advanced position from an end edge ofthe inlet port or from an end edge of the outlet port and a center ofthe driving shaft in a no-load state is termed a port reference line, aline that connects a center of the cam ring inner circumference side andthe center of the driving shaft at a high pressure when an eccentricityamount of the cam ring is a maximum is termed a high pressure camprofile reference line, a line that connects the center of the cam ringinner circumference side and the center of the driving shaft at a lowpressure when the eccentricity amount of the cam ring is a minimum istermed a low pressure cam profile reference line, and the threereference lines; the port reference line, the high pressure cam profilereference line and the low pressure cam profile reference line, are setto be substantially parallel to each other.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view in an axial direction of a vane pumpaccording to an embodiment 1.

FIG. 2 is a sectional view in a radial direction of the vane pumpaccording to the embodiment 1 (an eccentricity amount of a cam ring is amaximum).

FIG. 3 is a sectional view in a radial direction of the vane pumpaccording to the embodiment 1 (the eccentricity amount of the cam ringis a minimum).

FIG. 4 is a sectional view of a part of the vane pump in a no-load state(in a no-pump-drive state).

FIG. 5 is a drawing that shows a relationship between an angle between aport reference line M1-M2 and a cam profile reference line O_(c)-O_(R)and pump pulsation.

FIG. 6 is a schematic diagram showing a relationship between the portreference line M1-M2 and the cam profile reference line O_(c)-O_(R), ofa conventional art.

FIG. 7 is a schematic diagram showing a relationship between the portreference line M1-M2 and the cam profile reference line O_(c)-O_(R), ofthe embodiment 1 of the present invention.

FIG. 8 is a sectional view of the part of the vane pump according to anembodiment 1-1.

FIG. 9 is a sectional view of the part of the vane pump according to anembodiment 2.

DETAILED DESCRIPTION

According to the present invention, it is possible to provide thevariable capacity vane pump that reduces the decrease in pump efficiencyand the oscillation which are caused by the offset-shift of the drivingshaft.

In the following, the variable capacity vane pump of the presentinvention will be explained on the basis of embodiments shown indrawings.

Embodiment 1 Structure of Vane Pump

An embodiment 1 will be explained on the basis of FIGS. 1 to 7. FIG. 1is a sectional view in an axial direction of a vane pump 1. FIGS. 2 and3 are sectional views in a radial direction of the vane pump 1. FIG. 2shows a case where a cam ring 4 is positioned at an end in the negativedirection of a y-axis (an eccentricity amount of the cam ring 4 is amaximum). FIG. 3 shows a case where the cam ring 4 is positioned at anend in the positive direction of the y-axis (the eccentricity amount ofthe cam ring 4 is a minimum).

Here, in the drawings, an axial direction of a driving shaft 2 isdefined as an x-axis, and a direction in which the driving shaft 2 isinserted into first and second housings 11, 12 is positive direction ofthe x-axis. Further, an axial direction of a spring 201 that restrains arock of the cam ring 4 is defined as the y-axis (see FIG. 2), and adirection in which the spring 201 forces the cam ring 4 is the negativedirection of the y-axis. An axis orthogonal to the x-axis and the y-axisis a z-axis, and a direction where an inlet vent “IN” is located ispositive direction of the z-axis.

The vane pump 1 has the driving shaft 2, a rotor 3, the cam ring 4, anadapter ring 5, and a pump body 10. The driving shaft 2 is connected toan engine through a pulley, and rotates integrally with the rotor 3.

A plurality of slots 31 are radially formed at the rotor 3 and arrangedaround a periphery of the rotor 3. This slot 31 is a groove formed inaxial direction, and a vane 32 is provided in each slot 31. The vane 32is inserted into the slot 31 so that the vane 32 can move or extend inradial direction. In an inner radial side end portion of each slot 31, aback-pressure chamber 33, in which a pressurized fluid is provided, isformed for forcing the vane 32 outwards in the radial direction by thepressurized fluid.

The pump body 10 is formed of a first housing 11 and a second housing 12(a second member). The first housing 11 is formed into a cup-shapehaving a bottom, which opens to the positive direction of the x-axis. Ata bottom portion 111 of the first housing 11, a disk shaped side plate 6(a first member) is installed. The adapter ring 5, the cam ring 4 andthe rotor 3 are accommodated in a pump element accommodation portion 112that is an inner circumferential portion of the first housing 11, at thepositive direction side of x-axis of the side plate 6.

The second housing 12 is in liquid-tight contact with the adapter ring5, the cam ring 4 and the rotor 3 from the positive direction side ofthe x-axis. The adapter ring 5, the cam ring 4 and the rotor 3 aresandwiched between the side plate 6 and the second housing 12, and areheld by these side plate 6 and second housing 12.

On an x-axis positive direction side surface 61 of the side plate 6 andon an x-axis negative direction side surface 120 of the second housing12, inlet ports 62, 121 and also outlet ports 63, 122 are respectivelyprovided. These inlet and outlet ports communicate with the inlet vent“IN” and an outlet vent “OUT” respectively, then supply and exhaust ofworking fluid for a pump chamber “B” that is formed between the rotor 3and the cam ring 4 are done.

The adapter ring 5 is an oval-shaped ring member that is formed into asubstantially oval whose y-axis is major (longer) axis and whose z-axisis minor axis. The adapter ring 5 is installed inside the first housing11, and the cam ring 4 is installed inside the adapter ring 5. In orderfor the adapter ring 5 not to rotate in the first housing 11 during thepump drive, the rotation of the adapter ring 5 with respect to the firsthousing 11 is restrained by a pin 40.

The cam ring 4 is a ring shaped member that is formed into asubstantially perfect circle, and its diameter is substantially equal toa diameter of an inner circumference of the minor axis of the adapterring 5. Therefore, since the cam ring 4 is installed inside theoval-shaped adapter ring 5, a hydraulic pressure chamber “A” is definedbetween the inner circumference of the adapter ring 5 and an outercircumference of the cam ring 4 in a space outside the outercircumference of the cam ring 4. The cam ring 4 can therefore rock ortilt inside the adapter ring 5 in the y-axis direction.

A seal member 50 (a first seal member) is provided at a top end portionin the positive direction of the z-axis on an adapter ring innercircumferential surface 53. On the other hand, at a bottom end portionin negative direction of the z-axis on the inner circumferential surface53, a supporting surface “N” is formed. The adapter ring 5 supports thecam ring 4 and stops a movement in the negative direction of the z-axisof the cam ring 4 by the supporting surface “N”.

On the supporting surface “N”, the pin 40 (a second seal member) isprovided. The above mentioned hydraulic pressure chamber “A” between thecam ring 4 and the adapter ring 5 is divided into two hydraulic pressurechambers by this pin 40 and the seal member 50 at the negative andpositive direction sides of the y-axis respectively, and a firsthydraulic pressure chamber A1 and a second hydraulic pressure chamber A2are defined.

Here, since the cam ring 4 rocks or tilts while rotating on thesupporting surface “N”, each capacity or volume of the first and secondhydraulic pressure chambers A1, A2 is varied. However, the supportingsurface “N” at the negative direction side of the z-axis is formed to beparallel to ξ-axis that is defined by rotating the y-axis in a clockwisedirection with an origin point being a center. That is, the supportingsurface “N” slants or slopes at an angle γ in the negative direction ofthe z-axis as the supporting surface “N” extends in the positivedirection of the y-axis. And then, this sloping supporting surface “N”allows the cam ring 4 easily to rock or tilt in the positive directionof the y-axis.

An outside diameter of the rotor 3 is smaller than that of a cam ringinner circumference 41 of the cam ring 4, and the rotor 3 is installedinside the cam ring 4. The rotor 3 is provided so that an outercircumference of the rotor 3 does not touch the cam ring innercircumference 41 even when the cam ring 4 rocks and a relative positionbetween the rotor 3 and the cam ring 4 changes.

In a case where the cam ring 4 rocks and is positioned at the end in thenegative direction of the y-axis inside the adapter ring 5, a distance“L” between the cam ring inner circumference 41 and the outercircumference of the rotor 3 becomes a maximum. On the other hand, in acase where the cam ring 4 is positioned at the end in the positivedirection of the y-axis inside the adapter ring 5, the distance “L”becomes a minimum.

A length in the radial direction of the vane 32 is set to be longer thanthe maximum distance “L”. Therefore, the vane 32 always touches the camring inner circumference 41 while being inserted in the slot 31irrespective of the relative position between the rotor 3 and the camring 4. By this setting, the vane 32 always receives a back pressurefrom the back-pressure chamber 33, and the vane 32 liquid-tightlytouches the cam ring inner circumference 41.

Accordingly, liquid-tight spaces between the cam ring 4 and the rotor 3are always defined by the plurality of the adjacent vanes 32, and thepump chamber “B” is formed. Under a state where a center of the cam ring4 shifts from a center of the rotor 3 by the rock of the cam ring 4(i.e. the rotor 3 and the cam ring 4 are under an eccentric position),volume of each pump chamber “B” varies by the rotation of the rotor 3.

The inlet ports 62, 121 and the outlet ports 63, 122, respectivelyprovided in the side plate 6 and the second housing 12, are formed alongthe outer circumference of the rotor 3, and the supply and exhaust ofthe working fluid are done by the volume change of the each pump chamber“B”.

At an end portion in the positive direction of the y-axis of the adapterring 5, a radial-direction penetration hole 51 is formed. Further, aplug member insertion hole 114 is formed at an end portion in thepositive direction of the y-axis of the first housing 11. Then, a plugmember 70 formed into a cup-shape having a bottom is inserted into theplug member insertion hole 114, and an inside of the pump is insulatedfrom an outside of the first and second housings 11, 12 and theliquid-tight inside of the pump is maintained.

The previously mentioned spring 201 is inserted into the plug member 70,and is secured in an inner circumference of the plug member 70 so thatthe spring 201 is extendable and contractible in the y-axis direction.More specifically, the spring 201 penetrates the radial-directionpenetration hole 51 of the adapter ring 5 and touches or contacts thecam ring 4, then forces the cam ring 4 in the negative direction of they-axis.

The spring 201 is a spring that forces the cam ring 4 in the negativedirection of the y-axis, in which an amount of the rock of the cam ring4 becomes a maximum. Further, the spring 201 is the one that stabilizesthe discharge amount (a rocking position of the cam ring 4) during apump startup in which the pressure is not steady.

In the embodiment, an opening of the radial-direction penetration hole51 of the adapter ring 5 acts as a stopper that limits the rock in thepositive direction of the y-axis of the cam ring 4. However, the plugmember 70 itself could penetrate the radial-direction penetration hole51 and protrude from the inner circumference of the adapter ring 5, andthen act as the stopper for limiting the rock in the positive directionof the y-axis of the cam ring 4.

[Supply of the Pressurized Fluid to First and Second Hydraulic PressureChambers]

A through hole 52 is provided at upper portion in the positive directionof the z-axis of the adapter ring 5, at aside of the seal member 50 inthe negative direction of the y-axis. This through hole 52 communicateswith a control valve 7 via an oil passage 113 that is provided insidethe first housing 11. In addition, the through hole 52 communicates withthe first hydraulic pressure chamber A1 formed at the negative directionside of the y-axis, then connects the first hydraulic pressure chamberA1 and the control valve 7. The oil passage 113 opens to a valveinstallation hole 115 that installs the control valve 7 therein, and acontrol pressure “Pv” is introduced into the first hydraulic pressurechamber A1 with the pumping action.

The through hole 52 provided at the adapter ring 5 is formed at a middleportion of adapter ring's width in the axis direction, so that an outercircumferential surface of the adapter ring 5 acts as a seal surface andleakage can be reduced.

The control valve 7 connects to the outlet ports 63, 122 through oilpassages 21 and 22. An orifice 8 is provided on the oil passage 22, andan outlet pressure “Pout” that is an upstream pressure of the orifice 8and a downstream pressure “Pfb” of the orifice 8 are introduced into thecontrol valve 7. Then, the control valve 7 is driven by a pressuredifference between these “Pout” and “Pfb” and a valve spring 7 a, andthe control pressure “Pv” is produced.

Thus, since the control pressure “Pv” is introduced into the firsthydraulic pressure chamber A1 and this control pressure “Pv” is producedon the basis of an inlet pressure “Pin” and the outlet pressure “Pout”,a relationship between the control pressure “Pv” and the inlet pressure“Pin” is; control pressure “Pv” inlet pressure “Pin”.

On the other hand, the inlet pressure “Pin” is introduced into thesecond hydraulic pressure chamber A2 through a communication path 64.This communication path 64 is an oil path which communicates with theinlet vent “IN” and with the x-axis negative direction side surface 120in the second housing 12 then connects the inlet vent “IN” and thesecond hydraulic pressure chamber A2. The communication path 64 alwaysopens to the second hydraulic pressure chamber A2 irrespective of therocking position of the cam ring 4.

Therefore, the second hydraulic pressure chamber A2 is supplied with theinlet pressure “Pin” all the time. With this, in the vane pump 1 of thepresent invention, only a fluid pressure P1 of the first hydraulicpressure chamber A1 is controlled. On the other hand, a fluid pressureP2 of the second hydraulic pressure chamber A2 is not controlled, andthe fluid pressure P2 is equal to the inlet pressure “Pin” (P2=inletpressure “Pin”) all the time. With this, pressure leakage from thesecond hydraulic pressure chamber A2 side to the inlet port 62, 121 sideis reduced, and the decrease in the pump efficiency is suppressed.

[Rocking of Cam Ring]

When a total force of a biasing force in the positive direction of they-axis which the cam ring 4 receives from the pressure P1 of the firsthydraulic pressure chamber A1 and a force in the positive direction ofthe y-axis by the rock of the cam ring 4 in the positive direction ofthe y-axis by gravity becomes greater than a total force of a biasingforce in the negative direction of the y-axis which the cam ring 4receives from the pressure P2 of the second hydraulic pressure chamberA2 and the spring 201 and a biasing force in the negative direction ofthe y-axis on a fulcrum on the supporting surface “N” by a resultantforce that acts on the cam ring inner circumference 41 by a pumpinternal pressure, the cam ring 4 rocks in the positive direction of they-axis with a rolling-fulcrum (that is present on the supporting surface“N”) being a rotation center.

By the rocking of the cam ring 4, the eccentricity amount of the camring 4 becomes small, and an oil amount which is supplied from the inletports 62, 121 to the outlet ports 63, 122 in a unit time decreases, thenthe discharge amount is reduced.

As a result, a flow amount difference force of the orifice 8 decreases.The control valve 7 is then returned by the valve spring 7 a, and thecontrol pressure “Pv” is reduced by communication of the inlet pressure“Pin”, the pressure P1 of the first hydraulic pressure chamber A1communicating with the control valve 7 via the oil passage isconsequently reduced too.

When both the force in the negative direction of the y-axis and theforce in the positive direction of the y-axis, which act on the cam ring4, substantially become equal to each other, the both forces in they-axis direction, acting on the cam ring 4, balance out, then the camring 4 rests. The rock of the cam ring 4 is therefore stops, and acertain discharge flow amount is discharged.

Further, when the rotation increases, the pump discharge amountincreases and the pressure difference of the orifice 8 is increased. Thecontrol valve 7 then presses the valve spring 7 a and increases thecontrol pressure “Pv”, and the pressure P1 of the first hydraulicpressure chamber A1 is increased.

With this, by the rock and eccentricity of the cam ring 4 in the y-axisdirection, the discharge flow amount is regulated to such flow amountthat the pressure difference of the orifice 8 and a certain force F ofthe valve spring 7 a balance out. In this way, the eccentricity amountof the cam ring 4 is adjusted so that the pressure difference betweenthe upstream and downstream of the discharge orifice 8 is constant, andthe discharge flow amount of the pump P is controlled to be constant.

[Deviation of Positions Between Driving Shaft Center and Cam RingCenter]

FIG. 4 is a sectional view of a part of the vane pump 1 in a no-loadstate (in a no-pump-drive state). A center of the driving shaft 2 andthe rotor 3 is defined as O_(R), a center of the cam ring 4 is definedas O_(C).

In the present embodiment, the cam ring center O_(C) in the no-loadstate is set so that the cam ring center O_(C) is positioned at theinlet port 62, 121 side (the positive direction side of the z-axis) ascompared with the center O_(R) of the driving shaft 2. The rotor 3 isforced from the negative direction side of the z-axis by the outletpressure “Pout”, and the driving shaft 2 is bent and shifted in thepositive direction of the z-axis by this biasing force.

Thus, since the center O_(R) of the driving shaft 2 shifts in thepositive direction of the z-axis, the center O_(C) of the cam ring 4 ispreviously offset to the positive direction side of the z-axis ascompared with the driving shaft center O_(R). More specifically, byslanting the supporting surface “N”, a position in the z-axis directionof the cam ring 4 is set to be high. With this setting, even when thedriving shaft 2 is bent and shifted by the outlet pressure “Pout” duringthe pump drive, a stable discharge amount can be ensured (details willbe explained later).

[Cam Profile Reference Line]

The cam ring inner circumference 41 and the outer circumference of therotor 3 are substantially circular. Therefore when the cam ring centerO_(C) and the driving shaft center O_(R) are identical with each other,the distance “L” between the cam ring inner circumference 41 and theouter circumference of the rotor 3 is uniformly equal throughout theircircumferences.

When the center O_(C) of the cam ring 4 shifts from the center O_(R) ofthe rotor 3 and the driving shaft 2, the distance “L” between the camring inner circumference 41 and the outer circumference of the rotor 3is not uniformly equal, and the distance “L” takes a maximum vale and aminimum value on an O_(C)-O_(R) straight line. This O_(C)-O_(R) straightline is defined as a cam profile reference line O_(C)-O_(R).

The vane 32 is forced outwards in the radial direction by the pressurefrom the back-pressure chamber 33, therefore when the distance “L”varies, a protrusion amount of the vane 32 also varies. Because of this,the volume of the pump chamber “B” defined by the outer circumference ofthe rotor 3 and the cam ring inner circumference 41 and the vane 32 alsovaries depending on the distance “L”.

That is to say, in a case of a position of the cam ring 4 where thedistance “L” between the cam ring inner circumference 41 and the outercircumference of the rotor 3 is large, the volume of the pump chamber“B” is also large. In a case of the position of the cam ring 4 where thedistance “L” is small, the volume of the pump chamber “B” is small.Consequently, at a point before and after the distance “L” becomes themaximum value Lmax on the cam profile reference line O_(C)-O_(R) (at thenegative direction side of the y-axis on the O_(C)-O_(R) straight line)by the rotation of the rotor 3, the volume of the pump chamber “B”changes from the increase to the decrease. On the other hand, at a pointbefore and after the distance “L” becomes the minimum value Lmin on thecam profile reference line O_(C)-O_(R) (at the positive direction sideof the y-axis on the O_(C)-O_(R) straight line), the volume of the pumpchamber “B” changes from the decrease to the increase.

Since the rotor 3 rotates in the counterclockwise direction, when a vane32 a of the eleven vanes 32 crosses the cam profile reference lineO_(C)-O_(R) at the negative direction side of the y-axis, a volume of apump chamber Ba at the positive direction side of the z-axis from thecam profile reference line O_(C)-O_(R) increases. However, when the vane32 is positioned exactly on the cam profile reference line O_(C)-O_(R),the volume change becomes zero. And when the vane 32 is positioned onthe negative direction side of the z-axis after crossing the cam profilereference line O_(C)-O_(R), the volume changes to the decrease.

That is, each time the vane 32 a crosses the cam profile reference lineO_(C)-O_(R) at the negative direction side of the y-axis, the volume ofthe pump chamber Ba changes from the increase to the decrease. Likewise,each time the vane 32 a crosses the cam profile reference lineO_(C)-O_(R) at the positive direction side of the y-axis, the volume ofthe pump chamber Ba changes from the decrease to the increase. Withthis, each time the vane 32 crosses the cam profile reference lineO_(C)-O_(R), positive and negative of the volume change of the pumpchamber “B” are switched.

[Port Reference Line]

Suction and discharge in the pump chamber “B” change between the inletports 62, 121 and the outlet ports 63, 122. Positions of the vane 32 atsuction/discharge change point are first and second reference positionsM1, M2. The first reference position M1 is positioned at the negativedirection side of the y-axis, while the second reference position M2 ispositioned at the positive direction side of the y-axis.

In the embodiment 1, a space between the adjacent vanes 32 is 1 pitch,and a position of the first reference position M1 is ahalf-pitch-advanced position from end edges 62 a, 121 a (edge portionsof rotation direction of the rotor 3) of the inlet ports 62, 121.Likewise, a position of the second reference position M2 is ahalf-pitch-advanced position from end edges 63 a, 122 a (edge portionsof a reverse rotation direction of the rotor 3) of the outlet ports 63,122.

An M1-M2 line formed by these M1 and M2 is defined as a port referenceline M1-M2. Thus in the embodiment 1, each time the vane 32 a passesthrough this port reference line M1-M2, the suction and discharge of thepump chamber Ba are switched.

A Z-axis positive direction side section Bz+, which is located on thepositive direction side of the z-axis (the inlet port 62, 121 side) ascompared with the port reference line M1-M2, is a suction section. AZ-axis negative direction side section Bz-, which is located on thenegative direction side of the z-axis (the outlet port 63, 122 side) ascompared with the port reference line M1-M2, is a discharge section.

The vane 32 rotates from the end edges 62 a, 121 a of the inlet ports62, 121 to start edges 63 b, 122 b of the outlet ports 63, 122, therebypushing or forcing the working fluid on the suction side to thedischarge side. A volume of this pushing by the one vane 32 is expressedby the following expression 1.

$\begin{matrix}{V_{IN} = {\sum\limits_{\theta = O}^{\theta = \theta_{1}}{V_{IN}(\theta)}}} & \left\lbrack {{expression}\mspace{14mu} 1} \right\rbrack\end{matrix}$

The vane 32 rotates further from the end edges 63 a, 122 a of the outletports to start edges 62 b, 121 b of the inlet ports, thereby returningthe working fluid on the discharge side to the suction side. A volume ofthis returning by the one vane 32 is expressed by the followingexpression 2.

$\begin{matrix}{V_{R} = {\sum\limits_{\theta = 0}^{\theta = \theta_{1}}{V_{R}(\theta)}}} & \left\lbrack {{expression}\mspace{14mu} 2} \right\rbrack\end{matrix}$

When a pump discharge amount (volume) Vout per vane 32 is expressed bythe following expression 3,

$\begin{matrix}{V_{out} = {\sum\limits_{\theta = 0}^{\theta = \theta_{1}}{V_{out}(\theta)}}} & \left\lbrack {{expression}\mspace{14mu} 3} \right\rbrack\end{matrix}$

a total discharge amount (quantity) Qout is provided by the followingexpression 4.

$\begin{matrix}\begin{matrix}{Q_{out} = {N \cdot {\sum\limits_{\theta = 0}^{\theta = \theta_{1}}{V_{out}(\theta)}}}} \\{= {N \cdot \left( {{\sum\limits_{\theta = 0}^{\theta = \theta_{1}}{V_{IN}(\theta)}} - {\sum\limits_{\theta = 0}^{\theta = \theta_{1}}{V_{R}(\theta)}}} \right)}}\end{matrix} & \left\lbrack {{expression}\mspace{14mu} 4} \right\rbrack\end{matrix}$

A pulsation ΔVout that concerns noise of the pump P at this time is adifference between a maximum value and a minimum value of Vout(θ). Inbrief, this is a fluctuation amount of the pushing volume Vin(θ) (adifference between a maximum value and a minimum value of Vin (θ)) and afluctuation amount of the returning volume V_(R) (θ) (a differencebetween a maximum value and a minimum value of V_(R) (θ)). For reductionof the pulsation, these fluctuation amounts are required to be small.

When the port reference line M1-M2 and the cam profile reference lineO_(C)-O_(R) become equal to each other, the volume of the pump chamber“B” by the vane 32 changes from the increase to the decrease at thenegative direction side of the y-axis, and the fluctuation amounts ofthe pushing volume Vin (θ) and the returning volume V_(R) (θ) becomesmall (see FIG. 5).

When the cam profile reference line O_(C)-O_(R) deviates with respect tothe port reference line M1-M2 in a right upper direction, a proportionof the decrease in the volume of the pump chamber “B” rises at thenegative direction side of the y-axis, and the fluctuation amountincreases (FIG. 5). Conversely, when the camprofile reference lineO_(C)-O_(R) deviates with respect to the port reference line M1-M2 in aleft lower direction, a proportion of the increase rises, and thefluctuation amount increases (FIG. 5).

Hence, in order to stabilize the discharge of the vane pump 1, it isdesirable that the cam profile reference line O_(C)-O_(R) on which thepositive/negative of the volume change of the pump chamber “B” areswitched and the port reference line M1-M2 on which thesuction/discharge of the pump chamber B are switched should be as closeas possible to each other.

In particular, if the both lines are close to each other at the firstreference position M1 that is the switch position from the suction tothe discharge and at the second reference position M2 that is the switchposition from discharge to the suction, a discharge amount fluctuationis stable. Thus, it is desirable that the cam profile reference lineO_(C)-O_(R) and the port reference line M1-M2 should be as close aspossible to each other and also as parallel as possible to each other.

[Relationship Between Port Reference Line and Cam Profile Reference LineO_(C)-O_(R)]

FIG. 5 is a drawing that shows a relationship between an angle α betweenthe port reference line M1-M2 and the cam profile reference lineO_(c)-O_(R) and a discharge flow amount pulsation that causes a pumppulsation. An angle at high pressure is denoted by αh. An angle at lowpressure is denoted by αl. αh′ and αl′ are angles of the conventionalart.

FIGS. 6 and 7 are schematic diagrams showing a relationship between theport reference line M1-M2 and the cam profile reference lineO_(C)-O_(R). FIG. 6 is the conventional art (a case where the centerO_(C) of the cam ring 4 and the center O_(R) of the driving shaft 2 arepositioned on the port reference line M1-M2 in the no-load state (in theno-pump-drive state) is shown). FIG. 7 is the embodiment 1 (a case wherethe cam ring center O_(C) is positioned at the positive direction sideof the z-axis as compared with the port reference line M1-M2 in theno-load state is shown).

Here, in FIGS. 6 and 7, a thick solid line is the port reference lineM1-M2, a thick alternate long and short dash line is the cam profilereference line O_(C)-O_(R) (h) under a pump high pressure condition, anda thick broken line is the cam profile reference line O_(c)-O_(R) (l)under a pump low pressure condition.

In addition, a thin alternate long and short dash line N-N is a straightline that is parallel to the supporting surface “N” of the cam ring 4,i.e. a rocking locus of the cam ring center O_(C). A thin alternate longand two short dashes line Y-Y is a straight line that is parallel to they-axis. Therefore, the cam ring 4 rocks along the N-N straight line. Andas same as the supporting surface “N”, the N-N straight line is parallelto the ξ-axis, and its angle with respect to the Y-Y straight linebecomes γ.

The cam ring center O_(C) shifts in the y-axis direction by the rock ofthe cam ring 4. Then at the no-load and at the maximum eccentricity atwhich the pressure is the high pressure (see FIG. 2), the cam ringcenter O_(c) is widely offset from the driving shaft center O_(R) in thenegative direction of the y-axis. On the other hand, at the lowpressure, the eccentricity amount of the cam ring 4 is small and anoffset amount of the cam ring center O_(C) is also small. However, thecam ring center O_(C) is still offset from the driving shaft centerO_(R).

Here, when the pump 1 is driven and the pressure is produced in the pumpchamber “B”, the Z-axis negative direction side section Bz− becomes thehigh pressure, while the Z-axis positive direction side sectionBz+becomes the low pressure, with the port reference line M1-M2 being aboundary in the pump chamber “B”, and the pressure difference thereforeoccurs.

By this pressure difference, the rotor 3 is forced in the positivedirection of the z-axis together with the driving shaft 2, and thedriving shaft 2 is elastically bent in the positive direction of thez-axis. The center O_(R) of the driving shaft 2 also shifts to thepositive direction side of the z-axis due to this elastic deformation,then the deviation between the cam ring center O_(C) and the drivingshaft center O_(R) appears. A deviation amount becomes great at the highpressure, while it becomes small at the low pressure.

As a consequence, in the conventional art (FIG. 6), due to the elasticdeformation of the driving shaft 2 by the outlet pressure “Pout”, eachof the cam profile reference lines O_(C)-O_(R) at the high pressure andat the low pressure widely slopes with respect to the port referenceline M1-M2. Angles of the cam profile reference lines O_(C)-O_(R) at thehigh pressure and at the low pressure with respect to the port referenceline M1-M2, are αh′, αl′.

αh′ and αl′ are both large (αh′>0, αl′>0), and thus the cam profilereference line O_(C)-O_(R) and the port reference line M1-M2 arepositioned away from each other at the first and second referencepositions M1, M2 at which the suction/discharge are switched, and thisresults in an unstable discharge and the pulsation becomes great (FIG.5).

On the other hand, in the embodiment 1 of the present invention, the camring center O_(C) is previously offset to the positive direction side ofthe z-axis (the inlet port 62, 121 side) from the driving shaft centerO_(R), and the cam profile reference lines O_(C)-O_(R) (h), O_(C)-O_(R)(l) and the port reference line M1-M2 are set so as to be substantiallyparallel to each other at both the high pressure and the low pressure.

With this setting, the cam ring center O_(C) is previously positionedclose to the port reference line M1-M2, and the positions in the z-axisdirection of the cam ring center O_(C) and the driving shaft centerO_(R) are not widely separated from each other. Hence, the angle αbetween the cam profile reference line O_(C)-O_(R) and the portreference line M1-M2 during the pump drive becomes approximately zero atboth the high pressure and the low pressure, and the discharge amountfluctuation upon the switch of the suction/discharge becomes small.

That is to say, in the embodiment 1 of the present invention, since thesupporting surface “N” supporting the cam ring 4 is provided so that thesupporting surface “N” gradually separates from the port reference lineM1-M2 in a direction from the first hydraulic pressure chamber A1 to thesecond hydraulic pressure chamber A2 (towards the positive directionside of the y-axis), the driving shaft 2 is bent and shifted to theinlet port 62, 121 side (the positive direction side of the z-axis) ascompared with the cam ring center O_(C) at the maximum eccentricity andhigh pressure.

Thus, in order for the cam profile reference line O_(C)-O_(R) to be ableto be substantially parallel to the port reference line M1-M2, byraising a position of the rolling-fulcrum “Na” of the cam ring 4 to thepositive direction side of the z-axis, its position is shifted by anamount equivalent to the bend of the driving shaft center O_(R). At asmall eccentricity and low pressure, the bend of the driving shaft 2 issmall, thus this shift amount of the rolling-fulcrum “Na” could besmall.

With this, even when the driving shaft center O_(R) shifts in thepositive direction of the z-axis, the three reference lines; the portreference line M1-M2 on which the suction/discharge are switched and thecam profile reference lines O_(C)-O_(R) (h), O_(C)-O_(R) (l) at the highpressure and at the low pressure on which the positive/negative of thevolume change of the pump chamber “B” are switched, are substantiallyparallel to each other, then the pump discharge amount fluctuation isreduced at both the high pressure and the low pressure.

Here, although pressure noise generally increases in proportion to thepressure, since the cam profile reference line O_(C)-O_(R) (h) at thehigh pressure is the line that connects a cam ring center O_(C) (h) whenthe outlet pressure “Pout” is a maximum and the driving shaft centerO_(R), it is possible that the pump pulsation at the maximum pressure isreduced. With this, pulsation noise when the pump outlet pressure “Pout”is the maximum is reduced, and the pump pulsation as a whole is reduced.

Furthermore, the vane pump 1 of the present invention is a hydraulicpressure source of a power steering system, and the high pressurecondition (the outlet pressure “Pout” maximum condition) occurs when asteering wheel is fully turned or is turned in a vehicle stop state, andalso the low pressure condition (an outlet pressure “Pout” minimumcondition) occurs when the vehicle travels straight ahead. Therefore,since the pump pulsation is reduced at both the high pressure and thelow pressure, also in each of the cases where the steering wheel isfully turned or is turned in the vehicle stop state and the vehicletravels straight ahead, the pump pulsation is reduced.

Effect of the Embodiment 1

A variable capacity vane pump comprises: the pump body 10; the drivingshaft 2 rotatably supported by the pump body 10; the rotor 3 provided inthe pump body 10 and rotatably driven by the driving shaft 2; aplurality of vanes 32 radially extendably installed in their respectiveslots 31 that are arranged in the circumferential direction in the rotor3; the cam ring 4 rockably provided on the supporting surface “N” withthe pin 40 of the rock fulcrum being the center in the pump body 10 andformed into the ring shape also forming a plurality of pump chambers Bat the inner circumference 41 side of the cam ring 4 in cooperation withthe rotor 3 and the vanes 32; the side plate 6 and the second housing 12provided at both sides in the x-axis direction of the cam ring 4; theinlet port 62; 121 provided at least one of the side plate 6 and thesecond housing 12 and opening to the section of the pump chamber wherethe volume of the pump chamber increases; the outlet port 63; 122provided at least one of the side plate 6 and the second housing 12 andopening to a section of the pump chamber where the volume of the pumpchamber decreases; and the seal member 50 provided at an outercircumference side of the cam ring 4 and defining the first hydraulicpressure chamber A1 located at the side where the pump discharge amountincreases and the second hydraulic pressure chamber A2 located at theside where the pump discharge amount decreases in the space (thehydraulic pressure chamber A) outside the outer circumference of the camring 4, and the space between adjacent vanes 32 of the plurality ofvanes 32 is 1 pitch, the line that connects the half-pitch-advancedposition M1 from the end edge 62 a, 121 a of the inlet port 62; 121 andthe half-pitch-advanced position M2 from the end edge 63 a, 122 a of theoutlet port 63; 122 is termed the port reference line M1-M2, the linethat connects the center O_(C) of the cam ring inner circumference 41side and the center O_(R) of the driving shaft 2 at the high pressurewhen the eccentricity amount of the cam ring 4 is the maximum is termedthe high pressure cam profile reference line O_(C)-O_(R), the line thatconnects the center O_(C) of the cam ring inner circumference 41 sideand the center O_(R) of the driving shaft 2 at the low pressure when theeccentricity amount of the cam ring 4 is the minimum is termed the lowpressure cam profile reference line O_(C)-O_(R), and the three referencelines; the port reference line M1-M2, the high pressure cam profilereference line O_(C)-O_(R) and the low pressure cam profile referenceline O_(C)-O_(R), are set to be substantially parallel to each other.

With this, by setting the cam profile reference line O_(C)-O_(R) and theport reference line M1-M2 during the pump drive to be substantiallyparallel to each other, it is possible that the discharge amountfluctuation upon the switch of the suction/discharge becomes small.Accordingly, the discharge can be stabilized at both the high pressureand the low pressure, and the decrease in the pump efficiency and theoscillation can be suppressed.

In the following, a modification example of the embodiment 1 will bedescribed.

Embodiment 1-1

FIG. 8 is an example in which the definition of the port reference lineis changed. In the embodiment 1, the first and second referencepositions M1, M2 at which the suction/discharge are switched and thedriving shaft center O_(R) are positioned on the one straight line.However, in the embodiment 1-1, a case where these are not positioned onthe one straight line is shown.

Straight lines that connect the first reference position M1, the secondreference position M2 and the driving shaft center O_(R) in the no-loadstate respectively, are a port reference line M1-O_(R) and a portreference line M2-O_(R). When the eccentricity amount of the cam ring 4is the maximum, a straight line that connects the center O_(C) of thecam ring inner circumference side 41 and the driving shaft center O_(R)is a high pressure cam profile reference line O_(C)-O_(R). When theeccentricity amount of the cam ring 4 is the minimum, a straight linethat connects the center O_(C) of the cam ring inner circumference side41 and the driving shaft center O_(R) at the low pressure is a lowpressure cam profile reference line O_(C)-O_(R). Then, the threereference lines; the port reference line M1-O_(R) or the port referenceline M2-O_(R), the high pressure cam profile reference line O_(C)-O_(R)and the low pressure cam profile reference line O_(C)-O_(R), are set tobe substantially parallel to each other.

With this setting, the same working and effects as the embodiment 1 canbe obtained. In the embodiment 1-1, since an M1-O_(R)-M2 line is a bentline, the M1-O_(R) line or the M2-O_(R) line is the port reference line.By properly changing the definition of the port reference line accordingto the characteristic of the vane pump 1, an optimum dischargeperformance can be gained. Here, the M1-O_(R)-M2 line of the bent linecould be the port reference line as it is.

Embodiment 2

Embodiment 2 will be explained on the basis of FIG. 9. The basicstructure of the embodiment 2 is the same as the embodiment 1, thus onlydifferent points will be explained. In the embodiment 1, the cam ring 4is forced in the negative direction of the y-axis by the spring 201.

In contrast to this, in the embodiment 2, instead of the plug member 70,a piston 200 is provided as the plug member. Then, a space defined by aninner circumference of this piston 200 and a lid member 202 is a thirdhydraulic pressure chamber A3, and the third hydraulic pressure chamberA3 communicates with the control valve 7. With this, a pressure P3 ofthe third hydraulic pressure chamber A3 is controlled. This point isdifferent from the embodiment 1.

FIG. 9 is a sectional view in a radial direction of the vane pump 1according to the embodiment 2. The cup-shaped piston 200 having a bottomis inserted into a piston insertion hole 114 of the first housing 11 andthe radial-direction penetration hole 51 of the adapter ring 5 with abottom portion 210 facing toward the negative direction side of they-axis. Upon the insertion, the piston 200 is slidably fitted into thepiston insertion hole 114 in the y-axis direction with an outercircumference of the piston 200 and the piston insertion hole 114 keptin liquid-tight contact.

The piston insertion hole 114 is closed by the lid member 202 andliquid-tightly insulated from the outside of the pump, then the thirdhydraulic pressure chamber A3 is defined by the inner circumference ofthe piston 200 and the lid member 202. The third hydraulic pressurechamber A3 is located at an outer circumference side of the outlet ports63, 122.

The spring 201 is inserted into the piston 200 and is secured in aninner circumference of the piston 200 so that the spring 201 isextendable and contractible in the y-axis direction. One end of thespring 201 is secured to the lid member 202 at the positive directionside of the y-axis, and the spring 201 forces the piston 200 in thenegative direction of the y-axis.

With this, the bottom portion 210 of the piston 200 penetrates theradial-direction penetration hole 51 of the adapter ring 5 and touchesthe cam ring 4, then forces the cam ring 4 in the negative direction ofthe y-axis through the second hydraulic pressure chamber A2.

Further, in the embodiment 2, a communication passage 24 that connectsthe third hydraulic pressure chamber A3 and the control valve 7 isprovided inside the first housing 11. The communication passage 24 opensto the valve installation hole 115 that installs the control valve 7therein, and the control pressure “Pv” is introduced into the thirdhydraulic pressure chamber A3 with the pumping action.

In the same manner as the embodiment 1, the control valve 7 connects tothe outlet ports 63, 122 through the oil passages 21 and 22. The orifice8 is provided on the oil passage 22, and the outlet pressure “Pout” thatis the upstream pressure of the orifice 8 and the downstream pressure“Pfb” of the orifice 8 are introduced into the control valve 7. Then,the control valve 7 is driven by the pressure difference between these“Pout” and “Pfb” and the valve spring 7 a, and the control pressure “Pv”is produced.

Although the rocking action or working of the cam ring 4 is the same asthe embodiment 1, the supporting surface “N” supporting the cam ring 4slopes in the negative direction of the z-axis as the supporting surface“N” extends in the positive direction of the y-axis with respect to theport reference line (M1-O_(R), M2-O_(R) or M1-M2). For this reason, whenthe pump P is driven, the pressure acts on the negative direction sideof the Z-axis of the cam ring 4 in the negative direction of the Z-axisof the port reference line, and a resultant force of the pressure actsin the positive direction of the y-axis with respect to the rock fulcrumof the cam ring 4.

If an elastic force of the spring 201 against this resultant force issmall, self-eccentricity of the cam ring 4 occurs. Therefore, thecontrol pressure “Pv” is introduced into the third hydraulic pressurechamber A3, and thereby preventing the tilt of the cam ring 4 to thesecond hydraulic pressure chamber A2 side (to the positive directionside of the y-axis).

With this, the three port reference lines (M1-O_(R), M2-O_(R) and M1-M2)become substantially parallel to each other, then the pump pulsation isreduced. Moreover, it becomes possible to force the cam ring 4 in adirection of the maximum eccentricity (in the negative direction of they-axis) through the pressure. Thus even when a large discharge amount isrequired, the cam ring 4 can be shifted to the maximum eccentricity sideinstantly or quickly, and a desired pressure can be immediatelyobtained. For example, even when the steering wheel is turned abruptlyin the hydraulic power steering system, this can prevent a problem suchas unsmooth steering.

Although the invention has been described above by reference to certainembodiment of the invention, the invention is not limited to theembodiment described above. Further, design changes orengineering-change based on the embodiment are also included in theinvention.

In the embodiment 2, although the control pressure “Pv” is introducedinto the third hydraulic pressure chamber A3, the outlet pressure “Pout”could be directly introduced into the third hydraulic pressure chamberA3.

1. A variable capacity vane pump comprising: a pump body; a drivingshaft rotatably supported by the pump body; a rotor provided in the pumpbody and rotatably driven by the driving shaft; a plurality of vanesradially extendably installed in their respective slots that arearranged in a circumferential direction in the rotor; a cam ringrockably provided on a supporting surface with a rock fulcrum being acenter in the pump body and formed into a ring shape also forming aplurality of pump chambers at an inner circumference side of the camring in cooperation with the rotor and the vanes; first and secondmembers provided at both sides in an axial direction of the cam ring; aninlet port provided at least one of the first and second members andopening to a section of the pump chamber where a volume of the pumpchamber increases; an outlet port provided at least one of the first andsecond members and opening to a section of the pump chamber where thevolume of the pump chamber decreases; and a seal member provided at anouter circumference side of the cam ring and defining a first hydraulicpressure chamber located at a side where a pump discharge amountincreases and a second hydraulic pressure chamber located at a sidewhere the pump discharge amount decreases in a space outside the outercircumference of the cam ring, and a space between adjacent vanes of theplurality of vanes being 1 pitch, a line that connects ahalf-pitch-advanced position from an end edge of the inlet port or froman end edge of the outlet port and a center of the driving shaft in ano-load state being termed a port reference line, a line that connects acenter of the cam ring inner circumference side and the center of thedriving shaft at a high pressure when an eccentricity amount of the camring is a maximum being termed a high pressure cam profile referenceline, a line that connects the center of the cam ring innercircumference side and the center of the driving shaft at a low pressurewhen the eccentricity amount of the cam ring is a minimum being termed alow pressure cam profile reference line, and the three reference lines;the port reference line, the high pressure cam profile reference lineand the low pressure cam profile reference line, being set to besubstantially parallel to each other.
 2. A variable capacity vane pumpcomprising: a pump body; a driving shaft rotatably supported by the pumpbody; a rotor provided in the pump body and rotatably driven by thedriving shaft; a plurality of vanes radially extendably installed intheir respective slots that are arranged in a circumferential directionin the rotor; a cam ring rockably provided on a supporting surface witha rock fulcrum being a center in the pump body and formed into a ringshape also forming a plurality of pump chambers at an innercircumference side of the cam ring in cooperation with the rotor and thevanes; first and second members provided at both sides in an axialdirection of the cam ring; an inlet port provided at least one of thefirst and second members and opening to a section of the pump chamberwhere a volume of the pump chamber increases; an outlet port provided atleast one of the first and second members and opening to a section ofthe pump chamber where the volume of the pump chamber decreases; and aseal member provided at an outer circumference side of the cam ring anddefining a first hydraulic pressure chamber located at a side where apump discharge amount increases and a second hydraulic pressure chamberlocated at a side where the pump discharge amount decreases in a spaceoutside the outer circumference of the cam ring, and a space betweenadjacent vanes of the plurality of vanes being 1 pitch, a line thatconnects a half-pitch-advanced position from an end edge of the inletport and a half-pitch-advanced position from an end edge of the outletport being termed a port reference line, a line that connects a centerof the cam ring inner circumference side and the center of the drivingshaft at a high pressure when an eccentricity amount of the cam ring isa maximum being termed a high pressure cam profile reference line, aline that connects the center of the cam ring inner circumference sideand the center of the driving shaft at a low pressure when theeccentricity amount of the cam ring is a minimum being termed a lowpressure cam profile reference line, and the three reference lines; theport reference line the high pressure cam profile reference line and thelow pressure cam profile reference line, being set to be substantiallyparallel to each other.
 3. The variable capacity vane pump as claimed inclaim 1, further comprising: a pressure chamber that is provided on thesecond hydraulic pressure chamber side and forces the cam ring in adirection of a maximum eccentricity.
 4. The variable capacity vane pumpas claimed in claim 1, wherein: the supporting surface supporting thecam ring in the pump body is provided so that the supporting surfacegradually separates from the port reference line in a direction from thefirst hydraulic pressure chamber to the second hydraulic pressurechamber.
 5. The variable capacity vane pump as claimed in claim 1,wherein: the high pressure cam profile reference line is a line thatconnects the cam ring center when an outlet pressure “Pout” is a maximumand the driving shaft center.
 6. The variable capacity vane pump asclaimed in claim 5, wherein: the variable capacity vane pump is appliedas a hydraulic pressure source of a power steering system, and when asteering wheel of the power steering system is fully turned, the outletpressure “Pout” is set to be maximum.
 7. The variable capacity vane pumpas claimed in claim 5, wherein: the variable capacity vane pump isapplied as a hydraulic pressure source of a power steering system, andwhen a steering wheel of the power steering system is turned in avehicle stop state, the outlet pressure “Pout” is set to be maximum. 8.The variable capacity vane pump as claimed in claim 1, wherein: thevariable capacity vane pump is applied as a hydraulic pressure source ofa power steering system, and when a vehicle travels straight ahead, anoutlet pressure “Pout” is set to be minimum.
 9. The variable capacityvane pump as claimed in claim 2, further comprising: a pressure chamberthat is provided on the second hydraulic pressure chamber side andforces the cam ring in a direction of a maximum eccentricity.
 10. Thevariable capacity vane pump as claimed in claim 2, wherein: thesupporting surface supporting the cam ring in the pump body is providedso that the supporting surface gradually separates from the portreference line in a direction from the first hydraulic pressure chamberto the second hydraulic pressure chamber.
 11. The variable capacity vanepump as claimed in claim 2, wherein: the high pressure cam profilereference line is a line that connects the cam ring center when anoutlet pressure “Pout” is a maximum and the driving shaft center. 12.The variable capacity vane pump as claimed in claim 11, wherein: thevariable capacity vane pump is applied as a hydraulic pressure source ofa power steering system, and when a steering wheel of the power steeringsystem is fully turned, the outlet pressure “Pout” is set to be maximum.13. The variable capacity vane pump as claimed in claim 11, wherein: thevariable capacity vane pump is applied as a hydraulic pressure source ofa power steering system, and when a steering wheel of the power steeringsystem is turned in a vehicle stop state, the outlet pressure “Pout” isset to be maximum.
 14. The variable capacity vane pump as claimed inclaim 2, wherein: the variable capacity vane pump is applied as ahydraulic pressure source of a power steering system, and when a vehicletravels straight ahead, an outlet pressure “Pout” is set to be minimum.